Intersil Sensor Brightens Mobile Display

SAN FRANCISCO — After being off the tech radar in recent years, Silicon Valley-based Intersil has released a new Red, Green, and Blue (RGB) light sensor that aims to optimize screen brightness and improve resolution, battery life, and color quality for mobile device displays.

"Display consumes in excess of 40% of a phone's power budget today; improving power efficiency is a key element in optimizing devices," said Naresh Shetty, marketing manager for Intersil sensor products. "As screens get bigger, sensors and power are going to be a bigger issue with OEMs."

Intersil's new digital light sensor, dubbed ISL29125, communicates directly with a device's core processor to enable the automatic adjustment of display brightness based on changing light conditions to extend battery life, according to a release. ISL29125 runs at 70 microamps during device operation and less than half a microamp in standby, has an operating power supply range of 2.25 to 3.63V, and a variable conversion rate up to 16 bits.

"[ISL29125 provides] accurate information on light, it can tell if light is incandescent, florescent, or sunlight. The RGB sensor provides that level of control on different displays," Shetty said. "By monitoring ambient light, you can reduce or increase brightness based on room environment, thereby improving power consumption."

Intersil's new digital light sensor rejects IR in light sources allowing the device to operate in environments from sunlight to dark rooms while the integrated ADC rejects 50Hz and 60Hz flicker caused by artificial light sources. A selectable range allows the user to optimize sensitivity suitable for the specific application, the Intersil release continued.

"It's going to be very important that sensors get designed that give information to handsets to determine whether power needs to be given to display for optimization," said Gerry Purdy, chief mobility analyst with Compass Intelligence, a consulting and market research firm.

While sensors like ISL29125 will help optimize power consumption, Purdy added segmenting processes within handsets will be key for OEMs as phablets become more popular. Still, IHS iSuppli's Vinitia Jakhanwal said it's difficult to assess the total impact of RGB sensors on mobile devices.

"You may achieve good performance in one of the features, but what does it do to your device as a whole," asked Jakhanwal, mobile and immerging displays technology director at IHS. "It's not having a big impact on transmissivity, on your color. It can still support very high resolutions and provide you with power consumption savings."

Jakhanwal also questioned ISL29125's price point and power consumption compared to existing OLED solutions. Features that add a more than 10% premium but don't result in significant ASP increase cannot work, in her opinion.

At 1.65 mm x 1.65 mm x 0.75 mm, ISL29125's small form factor minimizes the size of the hole required to allow sufficient light through for accurate color measurement, improving overall industrial design. While it's unlikely that the sensor will be integrated into SOCs, Intersil's Shetty said the smaller geometry will be advantageous in future handset design.

Shetty also said the sensor can be integrated into camera modules to eliminate lag time during automatic white balancing. According to the company, ISL29125 could be integrated into a TV display to adjust display brightness and color consistency as the lighting conditions in a room changes.

The ISL29125 RGB sensor can be added to several applications for color temperature measurement accuracy, such as industrial color printers, thermostat displays and water quality testing devices, the release continued.

ISL29125 is currently in mass production and sensor-enabled camera solutions will be available in the second half of 2014. Shetty said he believes RGBs will achieve 35% of sensor volume by 2016 and replace existing ambient light sensor functions.

Both low-power and sensor technologies are trending heavily these days. Obviously, mobile devices are still booming for the fourth or fifth year in a row--so a confluence of interests makes sense here.

Of course, measurinig ambient light for the purpose of intelligently dimming and brightening the display backlight is important. Unfortunately, this article does not make clear we do this already. The measurement is typically done with a single sensor, most commonly a photodiode, that more or less mimics the spectral response of the human eye.

What these ambient light sensors (ALSs) do not do is measure red, green, and blue light independently. So the question is whether the Intersil sensor can produce sufficiently increased user satisfaction to justify its (presumably) higher cost. The answer to that question is not at all clear.

Can you in any way substantiate your first-sentence remark, "After being off the tech radar in recent years" re Intersil? It seems very unfair to them to make such a blanket statement, and then not back it up at all in the article. It's a "dig" at them without backup. (I have no vested interest or pro/con bias with respect to Intersil, I just don't like to see such broad statements made so casually.)

This is Naresh Shetty with Intersil. I wanted to take the opportunity to answer a couple of questions that were raised in the article. Today, ALS is used for ambient light intensity – as opposed to light source information – to manage brightness. Since device displays are translucent, a user's color perception changes depending on the source rather than intensity. RGB is currently the only way to identify light source (sunlight, fluorescent, incandescent, etc.) and therefore remains the only way to effectively adapt a display based on light. With respect to OLED solutions specifically, RGB is particularly useful for improving aging OLED display characteristics on large screens. Today, it's true that RGB is not as cost-effective for smartphone screens for the purposes of monitoring/adapting to OLED ageing.

The digital ALS has built in amplifiers, ADCs and I2C resources to interface directly to a SoC or any uC, making ALS implementation efficient, as compared to a standalone photodiode. ISL29125 do provide independent RGB information of the light source, which is used to measure correlated color temperature (CCT) along with Lux value.

My iPhone has an "auto-brightness" setting (although I cannot see any effect - perhaps my case blocks the sensor). What I don't understand from the article is how the RGB information would be used. Is the point that with light source information it would be possible to selectively brighten the colors that are being washed out by the ambient light while keeping the colors that are not present in the ambient light dim? How well does this work in practice? The human eye is very good at color correcting based upon the ambient light color temperature. If incandescent light is shifting the ambient colors towards the red end of the spectrum, the blue components of an image are "auto enhanced" and need not be so bright. If the Intersil technology utilizes this effect, it might save energy.